So I managed to snag a copy of Sketchbook Pro from the Autodesk booth at Siggraph today. I wanted to see how it compared with Photoshop, so I gave it a whirl.

I'm satisfied with the results that SBP can create, but it's lacking a few key tools such as Magic Wand and filters. It's very well designed for sketching though, and it hits the target really well. If you're looking for something that allows you to rapidly sketch on a tablet, this is the program for you. It duplicates a physical sketchbook fairly well. If you want full capability of pencils and pens, though, I'd hold out for Adobe Painter. That looks to be exceptionally well designed... and I'm seriously going to look into at least getting a Cintiq 21x to speed up my pipeline...